From publisher blurb:
Cosmic entities have always been part of the world, actually they are responsible for the existence of the world as a whole, spreading chaos and insanity into the corrupted minds. When one of three kingdoms decide to use this special cosmic connection to gain power advantage, they accidentally throw the entire world into a slow and inevitable apocalypse. Can the two other kingdoms with their armies stop the shadows of decay? Or perhaps only a
very special group of heroes can do it.
Shadow of Decay is a short scenario written to be playing using Fate Core Rulebook by Evil Hats Productions. It is a low magic medieval setting with huge influence of cosmic horror stories, where the players will not only be fighting physical beings but also their own corrupted minds.